This invention relates to dental resin compositions comprising polymerizable (meth)acrylate resins, their method of manufacture, and the use of such resins for restorative dentistry.
In recent years, materials used for dental restorations have principally comprised acrylate or methacrylate (“(meth)acrylate”) resins. Resins commonly used in most dental applications are multi-functional (meth)acrylates in combination with filler(s), which gives proper polymerization cross-linking and strength to satisfy the needs of a tooth restoration. An especially important multifunctional methacrylate resin is the condensation product of bisphenol A and glycidyl methacrylate, 2,2′-bis [4-(3-methacryloxy-2-hydroxypropoxy)-phenyl]-propane (“Bis-GMA”). Alternatively, Bis-GMA can be synthesized from the diglycidyl ether of bisphenol A and methacrylic acid. Especially when used as cements, these viscous resins are commonly used with multifunctional diluents such as tri(ethylene glycol) dimethacrylate (“TEGDMA”) and hexanediol dimethacrylate (“HDDMA”) to allow ready incorporation of filler(s) and enhance crosslinking and other functional properties of the compositions.
Dental compositions based on these resin materials have generally been formulated for hardness and strength, in order to provide a long-term tooth restoration. Conventional resin-based dental restorative materials, including those formed from di- and multifunctional (meth)acrylate cements, usually possess high compressive strengths (about 100 to about 450 Mpa) depending on the specific resin composition, filler type and amount, and the composition' intended used. However, in certain procedures temporary materials, that is, materials that are intended to be removed within a relatively short time period (e.g., one day to six months) are required. Such temporary materials do not require the hardness or strength of conventional compositions. Dental cements for use with temporary materials in particular do not need to be strong, and in fact, should be formulated for relatively easy removal. Accordingly, current temporary dental cements are acid-based materials such as zinc oxide-eugenol, zinc oxide-benzoic acid, calcium hydroxide-salicylic acid or its derivatives, and the like. These materials are weaker than permanent materials, and can serve the purposes of temporary cementation. However, they are also often brittle and, upon removal or breakage, leave unwanted residue on tooth surfaces.
Prosthodontic dental materials such as denture bases and denture base liners have also been manufactured using (meth)acrylate resins, particularly methyl methacrylate (MMA), methyl methacrylate polymers, ethyl methacrylate (EMA), and butyl methacrylate, in combination with a plasticizer. However, use of these methacrylates for dental restorative materials chairside is limited based on their odor. Methyl methacrylate monomer, for example, has a vapor pressure of 29 millimeter (mm) of mercury (Hg) at 20° C., EMA has a vapor pressure of 15 mm Hg at 20° C., and butyl methacrylate has a vapor pressure of 2 mm Hg at 20° C. The strong smell of these materials renders them unsuitable for placement directly in a patient's mouth and undesirable to work with in a dental laboratory.
There accordingly remains a need in the art for dental restorative materials, particularly cements, useful for temporary dental restorations. There particularly remains a need for materials that are not brittle and/or that can be cleanly removed from a tooth surface. There further remains a need for materials that can be used for laboratory manufacture of temporary restorations. It would further be advantageous for the materials to be free of objectionable odors at room temperature, and even more advantageous to package these materials in a convenient form, such as a kit or tray.